In semiconductor technologies, backside-illuminated sensors are used for sensing a volume of exposed light projected towards the backside surface of a substrate or sensor layer. The backside-illuminated sensors can be formed in the substrate and light projected towards the backside of the substrate can reach the sensors. However, without proper isolation, light targeted for one sensor pixel may also have a portion of the light directed toward other pixels, which can cause optical and electrical crosstalk among various sensor pixels.
Therefore, while existing methods of fabricating semiconductor devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect. In particular, improvements in backside illuminated sensors and/or the corresponding substrate are desired.